1. Field of the Invention
This invention relates to a high-density, integrated circuit module, which includes a plurality of stacked individual integrated circuit devices including complex geometric or serpentine interconnect rails for selectively interconnecting leads of the stacked integrated circuit devices to each other and to external circuitry, which includes strain relief.
2. Discussion of the Related Technology
One method of achieving an ultra high density integrated circuit module, which includes stacked individual integrated circuit devices, is to use external electrical interconnect rails to interconnect electrical leads extending from the stacked individual integrated circuit devices within the module. This method and high density module is described in U.S. Pat. Nos. 5,279,029 and 5,367,766, which are assigned to the common assignee of the present invention and are incorporated by reference herein for all purposes.
In applications where the high density integrated circuit module includes dissimilar integrated circuit devices, e.g. memory devices, microprocessor, DMA device, etc., or where the lead-to-lead spacing of individual devices is not uniform, there is a need for a non-linear signal path that provides selectable electrical interconnections between the dissimilar integrated circuit devices which make up the module.
In previous methods and apparatus for electrically interconnecting the leads of stacked integrated circuit devices within a high density module, the electrical interconnect rails associated with these prior art devices are typically linear, i.e. the leads in each respective column of leads in the stack of packages are electrically and thermally interconnected to a single linear rail. Thus, making an electrical connection only between alternating leads in a particular column of leads in the stack, or only between leads of every third or fourth device in the stack, is very, difficult. Leads from integrated circuit devices which are not to be electrically connected to the linear rails must be trimmed internally or externally so as to not contact the rail or, at the very least, bent away from the rails so a solder connection between the rails and the leads is not made. This requires a more complex and costly manufacturing process.
Previous methods which use non-linear rail interconnections, such as those described in application Ser. No. 08/377,578, entitled "High Density Integrated Circuit Module With Complex Electrical Interconnect Rails", assigned to the common assignee of the present invention and incorporated herein for all purposes, use non-linear rails having apertures formed therein for receiving leads to be connected to the non-linear rail. However, the non-linear rail is wider at the aperture portion than at other portion along the rail, since the aperture is completely surrounded by the rail. In applications where the lead centers of integrated circuit devices in the stacked module are closer together, the relatively large width of the rails at the apertures may make it more difficult to route additional non-linear rails between adjacent rails if the rails completely surround the aperture, thereby creating a more narrow space between adjacent rails.
Thus, the need exists for a non-linear rail design which enables complex electrical rails to be routed between adjacent rails as lead centers of devices get more narrow.